Gene retention refers to the process by which organisms maintain certain genes in their genome over evolutionary time, despite potential changes in the organism's environment, lifestyle, or genetic background. This can occur through selection for specific gene functions that are essential for the organism's survival, or through genetic drift that allows neutral or slightly beneficial genes to persist in the genome. Researchers studying gene retention aim to understand the factors that influence which genes are retained in an organism's genome and how gene retention contributes to the evolution and adaptation of species. This research can provide insights into the genetic basis of key biological processes, the relationships between genotype and phenotype, and the mechanisms by which organisms evolve and diversify.